The Federal Republic of Germany Patent Application P No. 30 28 956.6, traced back to the same applicant, suggested a method of the kind mentioned above in which the profiled rim section is clamped to a single bending core of round shape and bent around this bending core. This bending operation was based on generating the prestressing required for bending by friction between the brake shoe and the workpiece. A disadvantage of this method is that this bending operation requires a relatively large amount of time and equipment. For the rim to be bent it must first be prebent on a first piece of equipment, and then transferred to a second piece of equipment to complete the bending procedure. The transfer from one machine to another takes a relatively long amount of time and the use of two different machines was relatively costly. In addition, the friction-generated prestress of the workpiece was not easy to check.
Through German Democratic Republic DE-OS No. 26 50 357 another bending method has become known in which the rim section, originally in the shape of a straight, profiled extrusion, is pulled along a sliding block. But this method is disadvantageous in that the sliding block shows considerable wear which changes the shape of the profile and modifies the bending resistance in the course of time, so that mass production of uniform quality is not possible with one and the same tooling setup, because the sliding blocks must be replaced relatively often.
Moreover, the symmetry of shape of the motor vehicle wheel rim subjected to the bending operation is not ideal because in the above mentioned, known methods the bending process is always initiated from one side of the profiled rim section only and, starting from this side, is continued to the opposite end of the rim, in what is known as a unilateral bending operation. Such a unilateral bending operation can easily lead to out-of-roundness of the finish-bent rim, requiring a subsequent rolling operation to eliminate the out-of-roundness again.